Mention of the pledge of allegiance of a young child

Hisham bin Urwah narrates from his father that Sayyiduna Abdullah bin al-Zubayr and Sayyiduna Abdullah bin Ja'far (may Allah be pleased with them) pledged allegiance to the Prophet (peace and blessings be upon him) when they were both only seven years old. When the Messenger of Allah (peace and blessings be upon him) saw them, he (peace and blessings be upon him) smiled, stretched out his blessed hand and took the pledge from both of them.

Ja'far bin Khalid bin Sarah narrates from his father, who narrates from Sayyiduna Abdullah bin Ja'far (may Allah be pleased with them both), that he said: If only you had seen me, Ubaydullah and Qutham when we were children and were playing. Meanwhile the Messenger of Allah (peace and blessings be upon him) passed by us, and he (peace and blessings be upon him) said: "Lift this one up to me," and he seated me in front of him on his mount. Then he said about Qutham: "Lift this one up to me too," and he seated him behind him. Ubaydullah was dearer to Sayyiduna Abbas (may Allah be pleased with him) than (his brother) Qutham, yet he (peace and blessings be upon him) did not feel shy of his uncle (in taking Qutham rather than Ubaydullah). The narrator says: I asked: What became of Qutham? He said: He was martyred. I said: "Allah and His Messenger know best what good to bestow upon whom."
This hadith has a sahih (authentic) chain of narration, but the two Shaykhs did not record it.